Titanium oxides, such as titanium oxide represented by the general formula of TinO2n and lithium titanium oxide represented by the general formula of LiαTiβOγ are expected to be used in various applications due to the characteristics of titanium oxides.
For example, titanium oxide (IV) is expected to be used in applications, such as the electrode of a dye-sensitized solar cell, a storage battery that can be charged with light, an photoelectrode for hydrogen production by water decomposition, a pigment a coloring agent, a photocatalyst, an antibacterial material, water treatment technologies, and cancer treatment. Lithium titanate is expected to be used in applications like an electrode active material for power storage devices, such as storage batteries and capacitors.
However, these titanium oxides have disadvantages, such as poor electrical conductivity and absorption property capable of absorbing ultraviolet rays only. Hence, researches on complexs which have both the characteristics of titanium oxide and those of other substances, and which compensate the disadvantages of titanium oxide are being advanced.
For example, many researches have been made on the use of carbon having high electrical conductivity as a conductive aid for titanium oxide or lithium titanate (see, for example, Patent Document 1). Such researches are particularly active for power storage devices, such as lithium ion secondary batteries using metal compound particles for the positive electrode and the negative electrode, respectively, and lithium ion capacitors using active carbon for the positive electrode and using a material (e.g., graphene, and metal compounds) capable of reversibly adsorbing and desorbing lithium ions for the negative electrode. These power storage devices are applied as power supplies for information devices, such as mobile phones and laptop computers, and also applied for regenerative energy applications in vehicles, etc.